The Fixed-Term Employees (Prevention of Less Favourable Treatment) Regulations 2002 say that anyone employed under a succession of fixed-term contracts will become a permanent employee after four years "unless employment on a fixed term contract is objectively justified".

There is an exception for employees on a training / work-experience scheme arranged by the government or funded by the European Community.

In 2006 Ms Hudson began a fixed-term contract under such a scheme at the DWP. This was extended several times until Ms Hudson became a Support Officer in 2009. This was also a fixed-term contract, but not part of a training scheme.

In 2010 Ms Hudson argued that, having worked for more than four years under fixed-term contracts, she was a permanent employee. She was no longer working under a training scheme, so the exclusion did not apply.

The Court of Appeal disagreed, concluding that time worked under a training scheme does not count towards establishing the four year period.